A background art will be described by way of a hydraulic shovel, for example.
FIG. 9 illustrates a small hydraulic shovel called a mini shovel.
The hydraulic shovel includes a lower propelling body 1, an upper slewing body 2 mounted on the lower propelling body 1 so as to be slewable about an axis (central axis of slewing) O perpendicular to the ground, and an excavating device A attached to the front of the upper slewing body 2.
The lower propelling body 1 includes a car body (not illustrated) on which the upper slewing body 2 is mounted and crawler-type propelling devices 3 (only one of them is illustrated) attached to both left and right sides of the car body.
An engine room 6 surrounded by an upper frame 4 and an engine guard member 5 such as a panel or a bonnet is provided at a rear part of the upper frame 4 which forms the upper slewing body 2. An engine 7 and related devices thereof are provided in the engine room 6.
Moreover, a driver's seat 8 and an operation lever (not illustrated) are provided on the engine guard member 5. An operator operates the lever in a state of sitting on the driver's seat 8.
In FIG. 9, reference numeral 9 indicates a canopy which covers the driver's seat 8 from the upper side.
In this small shovel, when hot exhaust gas discharged from the engine is discharged upward directly from the engine room through an exhaust gas pipe (tail pipe), exhaust heat and exhaust sound blow directly toward the operator. Due to this, there is a problem in which the operation environment of the operator gets worse.
A feature disclosed in Patent Document 1 is known as an improvement technique related to a structure for discharging exhaust gas. This known technique will be described with reference to FIG. 10. FIG. 10 is a schematic view of a cross-section of the engine room 6 when seen from a rear side of the engine room 6.
A cooling fan 10 driven by the engine 7 and a heat exchanger 11 such as a radiator are provided in the engine room 6 on one end side of the engine 7. An intake opening 12 is formed in a portion on a side of an upper wall of the engine guard member 5 where the fan 10 and the heat exchanger 11 are formed, and a discharge opening 13 is formed in a portion on the opposite side of the upper wall. Outside air is introduced into the engine room 6 through the intake opening 12 with rotation of the fan 10 and passes through the heat exchanger 11, and cooled air (discharge wind) is discharged from the discharge opening 13.
On the other hand, a silencer (muffler) 14 is located on the other end side of the engine 7. The exhaust gas emitted from the engine 7 is discharged to the outside through the silencer 14 and an exhaust gas pipe (tail pipe) 15 connected to the silencer 14.
Here, in the known technique, a cylindrical duct 16 is provided at a position below the discharge opening 13 in the engine room 6 so as to extend in the up-down direction in a state where an upper end of the duct 16 is open to the discharge opening 13, and a lower end of the duct 16 is open to the inner side of the engine room 6. A distal end portion 15a of the exhaust gas pipe 15 is bent upward at the lower side of the duct 16 so that the distal end portion 15a is inserted into the duct 16 from the lower end of the duct 16.
By doing so, the discharge wind and the exhaust gas are guided into the duct 16, and both are mixed in the duct 16, whereby the temperature of the exhaust gas is decreased. After that, the discharge wind and the exhaust gas are discharged to the outside, and operating noise in the duct is reduced.
Although the known technique can better decrease the exhaust gas temperature and the operating noise than the conventional structure, the mixture of the exhaust gas and the discharge wind are discharged upward similarly to the conventional structure. Due to this, even if the known technique is applied in particular to the small shovel which does not have a cabin illustrated in FIG. 9, heat and noise still have a large adverse effect on the operator.    Patent Document 1: Japanese Patent Application Publication No. H3-229907